Rusty Russell wrote: >> To prevent a guest from stealing all the hosts memory pages, we can >> use these hashes to also limit the number of puds, pmds, and ptes. >> >> If the page is not pinned (currently used), we can set up LRU lists, >> and find those pages that are somewhat stale, and free them. This >> can be done safely since we have all the info we need to put them >> back if the guest needs them again. >> > > This is the same issue with 32-bit (one main reason why it's root-only). > In my case it's not too hard to add a shrinker (it would drop PTE pages > out of the pagetable of any non-running guest, just needs locking), but > we also want to avoid pinning in guest (ie. userspace) pages: for this I > think we really want a per-mm callback when the swapper wants to kick > something out. > > I imagine kvm will have the same or similar issues (they restrict their > pagetables to 256 pages per guest, which is simultanously too many and > too few IMHO). >
We have similar issues, but they are easily fixed since at most four pages are pinned per vcpu (sixteen with Ingo's cr3 cache). A per-mm swapper callback sounds great, especially when thinking about swapping regular guest pages, and even more in the context of nested page tables. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. _______________________________________________ Virtualization mailing list [email protected] https://lists.osdl.org/mailman/listinfo/virtualization
